Manufacture of zinc oxide



Jan. 20: 1925- H. A. GRINE MANUFACTURE OF ZINC OXIDE Filed Dec. 22, 1921 3 Sheets-Sheet l MHH-HH I il o ATTORNEYS.

Jan. 20, 1925- 1,523,416

' H. A. GRINE MANUFACTURE OF ZINC OXIDE Filed Dec. 22, V1921' 3 Sheets-Sheet 2 014/3 ATTORNEYS.

Jan. 20, 1925- 1,523,416

H. A. GRINE MANUFACTURE OF' ZINC OXIDE Filed Deo. 22, 1921 5 Sheets-Sheet 5 INVENTOR.

. l'h e /f ATTORNEYS.

Patented Jan. 20, i925.l

HARRY A. GRINE, 0F LANGELOTH, PENNSYLVANIA,

MANUFACTURE or zinc oxmn.

Application led` December 22, 1921. Serial No. 524,084.

To all whom t may concern Be it known that I, HARRY A. GRINE, a citizen of theUnited States, and resident of Langeloth, in the county of Washington and State of Pennsylvania, have invented certain new and useful Improvements in the Manufacture of Zinc Oxide, of which the following is a specification.

The invention relates chieiy to the manu facture of zinc oxide, which is adapted for use as pigment and for other colnmercial uses, the zinc oxide being produced from metallic zinc dross or fromother alloy cons taining zinc, or vfrom scrap or other metallic and apparatus suitable for zinc. While thel invention, asstated, refers particularly to the manufacture of zinc oxide, it may be considered more broadly as relating to the manufacture of oxides of metals whlch are volatilizable and readily oxidizable, from' the metals themselves or from alloys` containing the same. The invention includes both an improved and novel process use in practicing the process.

Zinc oxide, of a purity sufficient for use pigment or for use as a filler in rubber tlres and for other commercialu'ses, is commonly madev by a process of reduction and reoxi'dation of zinc ore on a so-called Wetherill .or pin hole grate hearth. It is not possible to utilize this apparatus for the production of zinc oxide from metallic zinc dross or zinc scra because the latter melt and become liqui before volatilizing, so that they cannot be chargeddirectly on such grates, since the molten metal filters through the coke or fuel used on the grate.

.is' volatilized in retorts through which a stream of non-oxidizing gas is' passed to re-v move the volatilized 'zinc to a small combus- .tion flue in which themetal vapors are 0x1- ldized, and' thence to a chamber collecting system for collecting the zinc oxide. This process is rather acomplicated one, has a comparatively smallcapacity, requlres expert operatives, and owing to the necessity of retreating the'product by heating it to give it a desirable color tone 41s more .expensive to carry out than the usual process of manufacturing zinc oxide pigment from the zinc ores. 1

An object of the present invention is to produce a process whereby the zinc dross, scrap zinc and the like, may efectively and economlcally be converted into zinc oxide su1table for pigment, or other commercial use s. Other objects of the invention relate to improved process steps and combinations, and the production of improved, a paratus of the character referred to, toget er with structural details and combinations'ofparts 1n the apparatus, all as will be more fully se't forth in the following specification and particularly pointed out in vthe appended claims.`

In carrying out the process the material comprlsmg or containing the metal is subjected to a preliminary distillation on a solid hearth whereby the zinc is volatilized until a crust or residue containing zinc oxide remains. This latter is thentransferred to a lVetherill grate hearth or the like, where ariane a reducing fuel such as coke is added and the f produced by the distillation of the zinc metal mingle therewith and are oxidized, the min- .gled hot gases and air being conducted away,

preferably, into a large combustion chamber and thence througha large cooling pipe li'ne into a filtering bag house. Preferably the solid hearth is placed directly above the pin hole grate so that the heat from the latter will serve to distill the metal on the solid hearth, partly by heating the latter `from below and partly by reason of the fact that the hot gases and air from the grate are carried around over the solid hearthinto contact with the material thereon.

In order that the invention maybe more l clearly understood attention is hereby directed to the accompanying drawings formingpart of this application and illustrating one form of apparatus included within the invention, and also illustrating the manner in which the improved process may be carried out. In the drawings- Fig'. 1 represents a front elevation, partly brokenaway, of a furnace having a plurality of compartments embodying one form of apparatusy included withinthe invention' 2 is a vertical section taken on line v2-'-2 of Fig. l; and

v 3, 3, of the various compartments of the furnace. provided with openings 4, 4, leading to the lower hearth level of the furnace, the openings 2 and 4 being provided with suitable doors 5, 5. The furnace is provided with a top arch 6 extending over the various compartments. The flue 7 is indicated as leading from one end of the Space 8 above the hearths 3, this flue being intended to lead to a large combustion chamber (not shown).

The furnace is divided into compartments by the division walls 9, 9, which are indicated as supported on channel members 10, the ends of which are supported in the outside front and rear walls of the furnace. The solid hearths 3 are supported between the division walls 9 and the end walls of the furnace, as shown, the division walls 9 preferably extending upwardly for only a short distance above the hearths 3. Charge openings in the top arch 6 are indicated at 11.

The lower hearths 12 take the form of suitable grates through which air may be blown, these grates preferably being of the type knowna as the Wetherill, or in hole grates. These grates are prefera ly supported by eye beams or the like 13, which extend through the division'walls 9 and into the end walls 1 of the furnace.

Each upper hearth 3 is preferably supported by an arch 14, the ends of which are supported by the end and division walls 1 and 9 of the furnace, the ends of these arches preferably abutting against suitable angular members 15, positioned within the walls,

the space between each upper portion 3 of a hearth and its supporting arch= 14 being filled with suitable refractory material. Each upper hearth 3 with its supporting arch is of a length, from front to rear of the furnace, somewhat less lthan the distance between the front and rear walls of the Vfurnace so as to leave vertical passages 16, as indicated in Fig. 2, at the ends of the upper hearths, through which the hot gases and` air from the lower hearths may pass upward. The upper surface of each upper hearth 3 is preferably somewhat concaved from front to rear, as shown in Fig. 2, so as to enable a shallow pool. of molten metal to remain thereon without running over the ends of the hearth.

Air for the operation of the furnace may bel conducted by a main air pipe 17 from which vertical connections 18 extend at in- The front and rear walls are alsotervals to lcarry air'into the chambers 19 below each lower hearth. The air supply may be regulated by suitable sheaver valves indicated at 20 in the downwardly extending pipes 18. v

Preferably water is maintained in the chambers 19 to assist in cooling the Wetherll grates and also to saturate the air with v 12, on which beds of live fire are obtained, y

after which coke or other reducing fuel may be charged on hearths 12 through openings 4 and the ire blasted until the entire furnace Vhas been brought to a bright ret heat, or about 1800 degrees Fahrenheit, A charge of zinc dross, or scrap zinc, orl other material to be treated is then Aput upon each upper hearth 3 together with sufficient fine coke -or anthracite coal to prevent excessive oxidation on the metal surface. Sufficient fine coke to cover the charges of metal may be dropped through the openings 11 in the upper arch and raked over the charges of metal. I have found that with a hearth of sixty-six square feet of area, for example, a charge of about four hundred (400) pounds of zinc covered with about twohundred and fifty (250) pounds of ine coke screening will constitute suitable proportions, the" invention, of course, not being limited to the use of such proportions or materials.

The charges on the upper hearths will be `heated by a direct transmission of heat through the hearths and also by the hot products of combustion and4 air from the lower hearths which pass around the .upper hearths through the end spaces 16.

In a short time volatilization of the metal begins and the vapors ignite over the charge, the oxidation of the metallic zinc vapors adding heat to the system. The charge on each u per hearthis rabbled from time to time with a hand rabble which may be inserted through an opening 2 to facilitate the volatilization and combustion of the zinc.

When the evolution of the zinc vapors from the char e has practically ceased the remaining resi ue, consisting of a crust comprising zinc oxide, and any foreign metals such as iron which are contained in the zinc dross or scrap, and the zinc coated coke, are raked down throu h' openings 16 on to the lower or Wetherhil rate hearths, and are raked over and into, te coke charge on this lllll llt) ieafiie hearth. A new charge of metallic zinc is now charged4 on to the upper hearth,vll together with a covering of fine coke as above described, and the operation on the upper hearth repeated, while the residue from the previous charge is being worked o on the lower hearth. At intervals of, usually, from four to six hours, the charge on each lower hearth having been worked off is. removed, in the same manner as when the ore is being worked, and a fresh charge of coke put in on the lower hearth. .The clinker from the lower hearths may be raked out and shoveled through openings 23 into the clinker cellar 24, where it may be carried away by cars. 'Ihe insertion of the fresh charge of coke on i the lower hearth is eHected shortly before the residue from the upper 'hearth is raked down thereon, a sufiicient time being allowed to permit the new coke charge on the lower hearth to become ignited before the residue from the upper hearth is raked down thereon.

On the lower hearth the reduction of the zinc oxide contained in the residue, in mixture with coke or anthracite reducing fuel,l

is completed, the zinc vapors bein subsequently oxidized as they rise su above the charge. The gases passing upwardly from the lower hearths through openings 16 will contain zinc oxide and all',

these Agaseous products mingling above the upper hearths 3 with the volatile vapors which rise above the charges on the upper hearths, the metallic zinc vapors from the upper hearths being oxidized to a very sub- Y stantial extent in contact with the hot gases and air from the lower hearths. The mingled ases are now carried olf through the flue indicated at 7 and into a large combustion chamber where any incompletely oxidized zinc or carbonaceous material is oxidized. From the combustion chamber the gases carrying the zinc oxide may be drawn by fan suction through a large cooling pipe line and discharged into a filtering bag house in the same manner as when operating on ores. These devices are old and I have not deemed it necessary toillustrate the same. In the pipe line the gases are suiliciently cooled to be discharged into the bag house lilter where the zinc oxide, for use .as pigment or otherwise, is filteredl from the gas and collected in the same manner asis now practiced with zinc oxide mjade from ores.

In the drawings I have shown the' upper preliminary distillation and hearths situated above the lower or Wetherill grate hearths, and in direct communication therewith through slots or openingsl .f at the ends of the upper hearths, this construction being deemed preferable by me because of the economy and eiiiciency secured thereby since the heat and gases from the lower hearths are thereby utilized to heat the upper ciently` oxidation hearths and carry oxide away from the upper hearths as rapidly as the same is produced. It should be understood, however, that I do not wish to limit my improved process or vapparatus to this particular arrangement, my invention covering any process or apparatus in which the metal is given a preliminary volatilization and oxidation and the residue removed from this preliminary operation to a finishing hearth, whereby practically all of the metallic zinc originally charged may be converted into zinc oxide suitable for pigment.

rIhe apparatus may also be used bv workin zinc ore on the lower .or 'vetherill hearths in place of, or together with, the residue which I have described as being raked down from the upper hearths to the lower hearths, in which case the hot gases and air from the lower hearths will heat the upper hearths and commingle with the zinc vapors from the upper hearths in the same manner l as previously described.

It 1s believed that the operation of the proce will entirely clear from the above description. lVhen the furnace is in operation, the charges of material including zinc oxide on the lower hearths will be subjected to reduction and subsequent oxidation while the metallic charges on the upper hearths will be subjected to distillation, the zinc vapors evolved being oxidized as they commingle with the hot Igases from the lower hearths. As the operation is completed on each lower hearth the elinker is raked out and removed, whereupon a new charge of coke will be laced on the grate and ignited and the resi ue from the hearth 3 above the same raked down thereupon, after which a fresh charge will be placed on the hearth 3. l

In the preferred form ofthe invention a battery or series of compartments, each containin an upper and a lower hearth, are used, t e hot gases from all of these. hearths mingling in the space above the upper hearths, which space forms a passage or chamber common to al1 the upper hearths. In such a system the temperature should be maintained as constant as possible throughout the furnace, the lower hearths naturally being a little hotter than the upper hearths, except at the times when the lower hearths are receiving coke. The whole furnace is maintained under suction, and accordingly will not be subject to leakage.

It should be understood that the invention is not limited to the exact details of constructipn and steps of process which have been articularly described but is as broad as is lndicated by the accompanying claims.

What I claim is:

1. The process of producing zinc oxide suitable Ifor commercial uses which comprises, subjecting metallic zinc to distillation and oxidation until a residue containing zinc oxide remains, then subjecting this residue to reduction and re-oxidation, and

collecting the vapors produced by both hearth, to distillation and oxidation until a residue containing zinc oxide remains, then removing this residue to a perforated grate, adding a reducing fuel, subjecting the residue to reduction and re-oxidation,

. and collecting the vapors produced by both operations.

3. The process `of producing zinc oxide suitable for commercial uses which comprises, subjecting metallic zinc to distillation and oxidation until a residue contain- `ing zinc oxide remains, then subjecting this residue to reduction and re-oxidation, mingling the vapors produced by both operations, and completing the oxidation of any incompletely oxidized zinc in the vapors.

j 4. The process of producing zinc oxide which comprises, subjecting a metallic alloy including a large proportion of zinc to distillation and oxidation until a residue containing zinc oxide remains, then subjecting this residue to reduction and re-oxidation, and collecting the vapors produced by both operations.

5. A process of producing a metallic oxide which comprises, subjecting a readily oxidizable, -volatilizable metal to distillation and oxidation until a residue containing the oxide of the metal remains, then subjecting this residue to reduction and reoxidation, collecting the vapors produced by both operations, and completing the oxidation of any incompletely oxidized portion of the metal in the vapors.v

6. The process .of producing zinc oxide suitable for' commercial uses whichv comprises, subjecting metallic zinc to distillation and oxidation until a residue containing zinc oxide remains, simultaneously subjecting, at a different point, a material containing zinc oxide to reduction and reoxidation, passing the hot gases and air from the last named operation above the point at which the first named operation is carried out into contact with the material there being treated, and mingling and collecting the vapors.

7. The process of roducing zinc oxide suitable for commerclal uses, which com prises, volatilizing metallic zinc, simultaneously subjecting, ata different point, a material containing zinc oxide to reduction and re-oxidation, and mingling the hot gases and air from the last named operation with the vapors produced bv the first operation to thereby oxidizve said vapors.

8. A process of producing a metallic oxide which comprises, volatilizing a readily oxidizable volatilizable metal, simultaneously subjecting, at a dierent point, a material containingthe oxide of the metal to reduction and re-oxidation, and mingling the hot gases and a-ir from the last named operation with the vapors produced by the first operation to thereby oxidize said va- POTS.'

9. The process of producing zinc oxide suitable for commercial uses which comprises, subjecting metallic zinc, covered by suiiicient reducing fuel to prevent excessive oxidation thereof, to volatilization, subjecting, simultaneously, a material containing zinc oxide to reduction and re-oxidation, and mingling the hot gases and air from the last named operation with the vapors produced byv the first operation to thereby oxidize said vapors.

10. The process of producing zinc oxide Suitable for commercial uses which comprises, subjecting a material containing zinc oxide to reductionA and re-oxidation,

passing the resulting hot gases and air above a solid hearth containing metallic zinc, volatilizing the latter, by the heat of the gases and by heat applied through the hearth and causing the zinc vapors thus produced to mingle with said hot gases and alr.

11. The process of vproducing zinc oxide suitable for commercial uses which comprises, subjecting a material containing zinc oxide to reduction and re-oxidation, passing the resulting hot gases and air above a solid hearth containing metallic zinc, volatilizing the latter, by the heat of the gases and by heat applied through the hearth, transferring the residue from the solid hearth, when thevolatilization is substantially completed, to the point at which the first namedv operation is carried out, re-

newing the charge of metallic zinc on the solid hearth, and-carrying on the operations at both oints continuously.

12. T e process of producing zinc oxide suitable for commercial uses which comprises, subjecting metallic zinc to a preliminary distil ation, removing the residue, con-l taining zinc oxide, to another point and subjecting it to reduction and re-oxidation, renewing the charge of zinc for the first opera.- f tion as often as the volatilization of the metal is substantially completed and transferring the residue to the point at which the second operation is conducted, and causing the hot gases and air from the second operation continuously to mingle with and oxidize the vapors produced by the first operation.

13. The process of producing zinc oxide suitable for commercial uses which comprises, subjecting metallic zinc to a preliminary distillation, While subjecting the residue from a previous distillation, containing zinc oxide, to reduction and re-oxidation at another point, utilizing the heat of said second operation to perform the first operation, and causing the hot gases and air from the second operation to mingle with the zinc vapors produced by the lirst operation to oxidize the latter.

14. In a furnace of the character de.

scribed, the combination of a solid hearth adapted to contain molten metal, a perforated grate hearth adapted to receive metallic oxide and fuel, means for blo-wing air through said grate hearth, means for conducting hot gases and air from above said grate hearth to a point above said solid hearth, and means for conducting gasesand air away from said point.

15. In a furnace of the character described, the combination of a solid refractory hearth adapted to contain molten metal, a pinhole grate hearth, adapted to receive metallic oxide and fuel directly below said solid hearth, means for introducing air under said grate hearth, means for conducting hot gases and air from above said grate hearth to a point immediately above said solid hearth, and means for withdrawing commingled gases at said point from the furnace, said solid hearth being adapted to be heated by the ,heat produced by said grate.

16. In a furnace of the character described, the combination of an enclosing structure, a perforated grate hearth, a solid hearth of refractory material above the same, the structure being arranged to provide passages by which gases from the lower hearth may pass above the upper hearth and by which material on the upper hearth may be pushed down on to the lower hearth' and said solid hearth being son'iewhat concaved and arranged to permit the pushing of material therefrom through said passages, to the lower hearth, means for introducing air under the lower hearth, and 'means for withdrawing gases above the upper hearth from the furnace.

17. In a furnace of the character described, the combination of walls and a covering member, a perforated grate hearth and a solid hearth therein, means for introducing air below said grate hearth and for withdrawing gases from the furnace from above said'solid hearth, the arrangement being such that said solid hearth will be heated by hot gases from said grate hearth, and hot gases from said grate hearth will pass above said solid hearth through passages on o pposite sides of said solid hearth, and mingle with gaseous products rising from said solid hearth.

18. In a furnace of the character described, the combination of walls and a covering member, a plurality of perforated grate hearths adapted for the reception of metallic oxide to be reduced, and fuel, and solid hearths therein the latter being in a continuous series separated by low division walls, means for introducing air below said grate hearths` means for conducting hot gases from said grate hearths above said solid hearths, the structure affording a con- Asuitable for commercial uses 'which comprises, placing a charge comprising metallic Zinc on a series of solid hearths maintaining fires, blasted by air, beneath the hearths, and conducting the hot gases and air from the res above the charges, to volatilize the zinc by the heat applied from below and above each charge, and to oxidize the zinc vapors, and causing the vapors from all the charges to commingle and be collected.

2l. The process of producing zinc oxide suitable for commercial uses which comprises, subjecting materials containing zinc oxide to reduction and re-oxidation at a plurality of points, passing the resulting hol gases and air above a plurality of so-lid hearths containing metallic Zinc, volatilizing the latter, by the heat of the gases-and by the heat applied through the hearths, and causing all the Zinc vapors thus produced to mingle as soon as produced, with said hot gases and air, and be oxidized thereby.

Signed at Langcloth. in the county of lashing-ton and Sta te of Pennsylvania this 16th day of December A. I). 1921.

HARRY A. GRIN E. 

